Bridging plug for wells and the like



Oct. 2, 1951 o. o. DALE ET AL BRIDGING PLUG FOR WELLS AND THE LIKE "Filed Nov. 28, 1947 2 Sheets-Sheet 1 22 29 fzvzva azzr'" a, 28 Uri: U. .3525 1717.17.43 M9 flu Oct. 2, 1951 o. o. DALE ET AL 2,569,457

BRIDGING PLUG FOR WELLS AND THE LIKE Filed Nov. 28, 1947 2 Sheets-Sheet 2 a J m J 1/ I ll/ l n W r fi E 9 2 fi r. 0% .Y L. I) Ill! 1/ lil! Ill/ll Ill/Wflfl/ll/ W P W J n6 4 w I) I I l 7 1/, I I 03 x 5 7& U. a 4 w 6 d G Ll p M Ill 1/ I! l/ Nl/ g I I .9 a,

. various purposes.

Patented Oct. 2, 1951 BRIDGING PLUG FOR WELLS AND THE LIKE Orie 0. Dale, Bakersfield, and John D. Chesnut, San Marino, Calif., assignors to International Cementers, Inc., Long Beach, Calif., a corporation of Delaware Application November 28, 1947, Serial No. 788,706

, .1 This invention relates to devices of the type commonly called bridging plugs; that is, 'plugs adapted to be introduced into and set in a well for the purpose of sealing off upper and lower sections of the well pipe or casing. Such plugs can be used to plug the interior of any passage, tube or pipe at any selected point. But as their major use is in oil wells, thev invention will be described with that use in mind; its use in analogous situations will be obvious.

- Bridging, or other plugs are used in wells for In some instances they are constructed so as to be not only settable in the selected location but also to be removable by some special operation and/or special tool. For simplicity of structure, and especially where the plug is used as a temporary bridge to support a plug of poured cement which is subsequently drilled out the plugs are commonly constructed to be drilled out rather than removed intact. The present invention relates primarily to that simple type of plug that is, a plug adapted merely to be selectively set in position, usually to form a temporary base for building a bridge or plug of cement, plastic, sand or the like.

The essentials of the simple drillable form of bridging plug are as follows. The body or frame is preferably made of some easily drillable material and is provided with a passage either around it or through it (or both) to allow the plug to be lowered in a casing containing well fluid. Those passages (both are usually used) are closed against relative. downward fluid movement by valvular means; usually an upwardly facing flexible sealing cup and an upwardly opening check valve. If the plug is merely to be set against downward movement in the casing, the plug is equipped with some kind of casing engaging elements which,when released to set, are forced into casing engagement by relative downward movement of the plug. Wedge slips which move out by relative upward movement on the plug body are commonly used. And if the plug is also to be set against upward movement in the casing, as

is desirable, oppositely acting slips are also used. These latter slips, which set only by relative upward movement of the plug in the casing, do not have to have any special control means; but it is necessary, in order to insert the plug to the setting point, that the slips which look the plug against downward movement be held from action.

and released only when the setting point is reached. The problem of setting the plug involves primarily the problem of controlling those slips. 1

Various means, usually involving special setting tools and/ or requiring that the plug be lowered on a pipe or rod, have been proposed to solve that problem. The primary characteristic of the pres-;

ent invention lies in its provision of an exception-.

, 16 Claims. (01. 166-13) which ally simple and reliable set-controlling arrangement which is easily operated without the need of any special tools or fixtures, which enables the. plug to be lowered and operated on a simple flexible line, and which in general provides a plug that is easily and cheaply manufactured in all required sizes.

And a further feature of the invention has to do with the control of a sealing member (e. g. valve) which may be used to close the plug pas sage against relative upward movement of fluid through the plug. It is desirable that the set plug be sealed against fluid passage either up or down, and the present invention applies the same simple settingcontrolto such a valve as to the slips.

These controls, in general, involve detent members which lie in the path of setting (or closing) movement of the slips (or valve) and which are simply pulled out of their detaining positions by a pull on the lowering line. The detents are, in effect, mere extensions of the lowering line; they may preferably be, as shown here, integral parts of the lowering line. The act of pulling on the lowering line simple pulls the detents of place and. removes them with the line from the well.

Another feature of the invention in its preferred form lies in its provision of a skeleton plug body which facilitates low cost manufacture of plugs of different sizes, using standardized parts. The simplicity of the setting controls, involving no relative movable parts which must fit other parts, makes it possible to utilize a simple skeleton body which can be of any size. I

The invention is described in preferred and illustrative form in the following description, with reference to the accompanying drawings in Figs. 1 and. 2 are vertical longitudinal sections respectively showing the plug as it is lowered in the well, and set in the well, these sections being taken as on line ll of Fig. 3;

Fig. 3 is a horizontal section on enlarged scale on lines 3-3 of Figs. 1 and 4;

Fig. 4 is an enlargement of a portion of Fig. 1;

Figs. 5 and 6 are vertical sections showing modifications;

Fig. '7 is a schematic view at reduced scale showing a typical arrangement for lowering and controlling the plug on a flexible line.

In the drawings, Fig. 1 illustrates one illustrative form of the plug in the condition in 3 the lowering and control lines away. Figs. 1 and 2;-illustr.ate a form of :plug in which the plug passages are sealed merely against relative downward passage of well fluid, cement or other bridge-forming material, when the plug is set. Figs. 5 and 6 illustrate modified forms in which the flow passages are sealed against relative fluid flow both downwardly and-upwardly.

As has been stated, the .plug and its setting controls are of such form that the:plugmay 'be lowered and controlled solely through the medium of a simple flexible line or wire. Such .a flexible line is illustratively shown in Fig. '7 at l I, continued (in the form of Fig. 1) by the extension lines I la which form in full effect direct ex- :tensions or integral portions of the supporting line -I I. Were it not for the fact that the plug is preferably mainly composed of i'light weight -materials which are easily drillable, lines .Ha.

per-end of the sinker bar (weight) as 'shown in Fig. 7. The weight, whatever it is, may be-regarded as being included in the line H, Ila. Although sufficient weighttmight'be added directly to the plug (e. g. by the simple expedient of placing some ..heavy material .in the upper sealing "cup 42) it is preferred to include the weight in the supporting line so that it may be withdrawn when the plug is ;set.

,It is a feature of .the. invention ,that. such a simple. lowering. and control .means as a flexible 1 line may. .be .,used but the invention is .not at all limited against the plug being suspended from .and lowered von..a rod or pipeor the like. ..For

instance, the extension lines .I la, instead of-being joined to the primary line 11, may beconnected to any suitable-lowering rod or pipe.

Asshown inthe drawings, the bodyofthe plug is preferably made. up of upper and lower-head plates 20- and 2 I ofdiameters somewhat.- smaller than the interior of the pipe in which theplug .-is:intended to;operate,:and of -a plur ality ofupright slip orgripper guiding :members 22 which -.extend, vertically between the upper and lower disks 20 and 2! :and are secured to :them .by *any suitable means, such as the screws or'bolts 23 in Fig. 3. These slip guides may be of any :suitable number,:shown as three inthe drawings.

Each slip guide preferably carries a set: of two slips, one setting by relative upward movement and the "other-by relative downward movement. The :slips maybe of any-suitable form. Wedges sliding ininclined guide ways are usually used. But for simplicity of manufacture involving no requirement for nicelyfltting parts, slipsor gripping members in the form of 'rollersareihere preferred.

In each slip-guide the relative positions of the upwardly setting and downwardly setting slips or gripping members may bezas desired; but for several;reasons, particularly that of-strength in the .designqof .the slip guides, it is preferred to argrange thepairs ofslipsin eachguideso thatthe' slip which sets by relative upward movement on the body (holds the body against down move- ,mentin the casing) is located inJthe upper part bottom adjacent the upper and lower plates and Z1. Witha given amount of material, the arrangement thusmakes the slip guide strongest as a beam to resist inward crushing forces due to the wedging action of the slips or grippers.

As shown in the drawings each slip guide com- -;prises:an upper and a lower channel formation having a back wall or 'web and 'two side walls or flanges 26; 'a central strengthening-web :21,

and end formations, suchias ears 28,:by which 'theguide'is securedito the top'and 'bottom":plates. Each channel formation tapers, upwardly or downwardly from the central web: 2l1, and 'zthe channel-side walls 26 'have'slip guiding grooves 29. Grooves29, and back wall2'5, of'theupper channel formation extend upwardly and outwardly'from the center'of'the guide member; and grooves 29 and theba'ck wall of' thelower channel formation extend downwardly'and outwardly from the center.

A slip or gripper of the roller type is mounted in'each channel formation. As illustrated, each gripper comprises a small roller "39 loosely mounted on a transverse spindle pin -'3I -whose ends extend beyond the side "faces of the roller and into theguid'e grooves 29. 'It is"not"neces sary that the spindles fit theguide grooves-at all accurately or snugly. The axial 'or width dimension of the roller "30' is such thatit fits between the two opposite'channelwal1s26closely enough that 'the spindle cannot "coclr'to "any appreciable angle in the guide "grooves. The

primary purposes of the projecting pin in the guide grooves is to prevent the 'rollerfromialling out of the groove, and also to;make.simple provision for the attachment of the springs which urge the rollers toward their gripping positions. The engagement of thepins in the guide grooves may be used forthe purpose of forcing the rollers outwardly as they move longitudinally'o'f the guides. On the otherhand the rollers "may be of such size that theirperiph- 'eries roll on'the inclined .back walls '25.

It will be noted that the lowerv rollers 30 could be allowed simplytofall un'derjgravity into their lower pipe gripping.. .positions. It is preferred however to apply springs to those rollers aswell as to theupper rollers, :to -move them into theirgripping positions. Tension. springs .are preferred for the upper rollers,.andsosimilar springs are used for the lower rollers. Thus, in

'jboth cases tension springs are mounted in Jthe several grooves 29 and at one end are .at- 'tached at 35a to the projecting ends .of roller ..spindles.38,-and at their otherendsareattached, .in any suitable .manner as indicated at 351), to

.is-mounted'on the upperfaceof plate 20, and a :ball cage d3 of any suitable designis mounted :upon the cup. :CageGSlis-Qf any suitable design that prevents valve 4| from becoming an up--' wardly closing one. For instance, as shown'in Fig. 2 it may have openings 44 through its side walls.

The effective diameter of the plug shown in the drawings depends solely on the diameters of upper plates 20 and 2| and of sealing cup 42. Thus, a plug of any chosen efiective diameter may be made up by using standardized guide and roller assemblies, and mounting them on upper and lower plates of the chosen diameter, and using a sealing cup of the correct diameter. As the sealing cups of various diameters are articles of standard manufacture, plugs of any chosen effective diameter may be made up simply by assembling standardized guide and roller assemblies with the chosen sealing cup and with upper and lower plates of suitable sizes.

Whatever the diametral size of the plug may be, it will be seen from the drawings that the plug body is generally of a skeleton form and that a free open space exists in the central part of the body inside the several guide members. The suspension and control wires Ha are easily strung through this open space and their lower ends are easily put into their locations directly above the spindles of upper rollers 30. As shown in Figs. 1, 3 and 4 the suspension and control wires Ha are strung down through valve cage 43, around ball GI and through plate opening 20-. From there they extend on down and pass through perforations 50, the locations of which are best seen in Figs. 3 and 4. Each perforation 5D intersects one guide groove 29 just above the roller spindle 3| (of the upper rollers 30) when those rollers are in their lowermost positions. The wire I la, crossing the groove 29 above the roller spindle, is effective in holding the roller down against the upward pull of its springs. Although two such hold-down wires could be used for each upper roller at both ends of its spindle, one is found to be sufiicient. The final end of each wire Ha is passed through the portion of perforation 50 which lies outward- 1y of groove 29 and the terminal wire end is finally bent down as shown at llc either against the outer surface of the guide member or into a superficial recess which is indicated at lid.

The purpose of the terminal bend in the wires is to releasably hold the wires in place in such a manner as to require a fairly definite upward I pull on the wires in order to pull them out of the plug structure. .Any other suitable means or arrangement could be used. For instance, it will be noted that each wire Ila passes through several bends in its extent from the top of the plug to its lower end. As an illustration, there may normally be a rather sharp bend at the point indicated as He in Fig. 4; and the bend at that point, together with the frictional contact of the wire in perforation 5U, and the frictional contact with the upwardly pressed roller spindle 3|, might be utilized as the releasable means for holding the wire in place until a definite upward pull is exerted. Or, the terminal bend at He might be made such as to more or less positively lock the end of the wire in place, and the wire could have a weakened portion adjacent that bend; and then the weakened portion would become the definitely releasable means of holding the wire in place. It has been found in practice however that the simple holding arrangement shown in the drawings, and constituting mainly the terminal bend in the wire, is reliably suflicient for the purposes. It

, 6 is only necessary that the releasable holding of the wiresbe strong enough to reliably support the weight of the plug dfilingtll lowering operationsi'" The plug is very light (being preferably composed of metal such as magnesium or aluminum in order to be easily drillablel and consequently the relative margin between the weight thrust which the wires normally have to support, and the upward pull which can be easily exerted on the wires, is very large. Such a simple'holding means as has been illustratedl therefore sufiices.

As shown in Figs. 1 and 7, where a line-ineluded weight is used to force the plu down, the sinker bar H I may have a fitting H2 threadedly attached to its lower end. :The fitting H2 has a:

lower end recess H3 that fits over valve cage 43 with the:lower edge of the fitting resting directly on the plug. Wires Ila extend upwardly from the valve cage through holes ll 4 in the fitting; and then havev their upper ends secured in any suitable manner, as by simply tying them around.

the shank of I I2. The plug is thus held up closely against the weight fitting with no looseness Ice-- tween the plug and the. weight. Similar means can be used .for attaching the plug to a dump; or to a length of cable-suspended pipe, or to the lower end of a stringer tubing, etc;

The operation of the device of Figs. 1 and 2) follows from the for going description. In preparation for lowering in the well the suspension. and control wires Ila are put in place to hold. the upper gripper rollers 30in their lowermos positions. On stopping the downward movement at the selected setting point, or on the inception of an1 upward pull on the suspension line, the lower grippers 30 set automatically to hold the plug against further'upward movement. Con-' tinued upward pull on the suspension line ll then pulls the suspension and control'wires Ha away from their positions over the spindles of the upper gripper rollers.

' equipped with valvular means for sealing the plug against both downward and upward movements of fluid. The device as there shown is the sameas that shown in Figs. 1 to 4, with certain additions. The same numerals are applied to duplicate parts of Fig. 4 and those duplicate central opening 21b with which both plate 2| (Figs. 1 and 2) and plate 2|5 are provided. A valve cage 435 encloses ball M5, and the ball valve is normally urged up by valve spring Ha.

.When-this valve closes onto its seat around opening Zlb it prevents relative upward movement of fluid through the plug. In .order to hold theball off its seat during lowering of the plug through well fluid, awire or wires which in efiect The upper gripper rollersthen immediately move up to their grip-- ping positions of Fig. 2 where they prevent down--' ward -movement of the plug. Removal of the. suspension and control wires also pulls them past aseaa brmeeesr form cit-tensions ":of the rv other suspension; and i; control' wirlesmay be inserted between' the ball and its'e'seatk Thus, for 'instanca'rtwo additional suspension and contr'ol. wires ||-'*:(in 'addition' to the' three wires Ha) may 'be "added to'the group of'suspension and control wires. 'These two additional wires past upper ball'4'llike the others and then ex tend on down and have their terminal-ends, at 5a insei ted'rbetween'lower-bail 4 5: and its seat. These terminal ends may be bent'somewhat as illustrated under the lower face of plate'Zl5" so that those bends also function "as releasable holding'7or' detent means fort-the suspensionandxccontrol -wires; The extrawires: ||'5- arepulled '1 out of place and pulled awayffrom'the: plug in r Y the same 'manner-easrbefore describedyiallowing ball 4|5 -to seat at the same time'thatithe'upper' expandinggripper rollers are allowed tomove to position 'to' lock the plug againstidownw-ard movements-F In- 'Fig. '5'Qall1th'e Wiresel |afand ,||5'i' 1' are shown simply asriextendin'gabove theplu'g, to be connected in any of "the manners before 1' described. i

Fig. 6 shows another variant form which in major respects is raiduplicate of the: design shown in Figs.'l and '2' *Duplicat'einumerals are'applied to duplicate parts, and onlyrthe changedeorfaddi tional features will-be describedaii In thislform otEig; fi'tlieiower plate'zl' is the 30 same asplatefZ I? of Fig. 11' :Therdownwardly fac:-' ing flexible sealing cupc4'26tis attached" to-"the upper headwplate-iZO'G under thea'upwardlyi facing cup 42san'd'ithe walve cage=436zz-The upwardly seatingz valvefl'fif is locateddn the upper valve 5 cage 4%, along with-"the downwardly seating:

ball valve .4lp' That ddwnwa'rdlyzseating'ball '4:|

is the same ima'ction as ba1l4-| of Figsil and 2; except ith'at: it" is-urged downwardly not only by gravityabut-also by the sprin 4|bt.which* lies between the-two zballsr-andtals'o"urgesba1l"4|6 upwardly towarddts rseat which surroundsthe' opening 43bzrat the upper end'of 'cagei36i In Fig. 6 cage 4361 is aneimperforate 'cage sdthat fluid can only passthrough'it vertically-by passe mg through the upperopenmg'43b and the lower por tion 10f Said wire opening in the upper-bodyplateiiu. The sus'-" pensionsand control wires I la are the same 'wires as shown in Figsrl and 2. tThey perform-' the'" functioniz of releasably :holdlngthe Jupper rollers 59 30 downg'a'si-before explained; and: they not onlyv pass around the lower ball 4|, but also around my the upper'ball 4|6to. hold that zballwdown' off its seat during lowering of the plugz-throughwell' fluid. J

The operation :of this form *is 'theisameas be fore described? Theplug can be lowered through well fiuidwhile-ball; 4|6 isheld off/"it's seatyan'd. 3 when thezplug is-set: by the operations before described thelremoval of the wires releases both valve balls 4| and 4| 6 toseat and'to seal theepassage through the:plug against both'upward and downward-relative movements of fluid;

In the foregoingdescription and in the fol* lowing tclaims the? directional ---terms 'down, I up and fverticalf andxsimilar terms, are used respectively and collec'tively in? the senses of the direction in which theplug is inserted inthe'pipe 1' or other/opening 'or passageyand'the opposite directional Regardless ofithe nature of the? specific z means by which the plugis loweredandsetrinithe well whether: that 1 means involves a string of pipe; or a simple flexible Wireor-cablaweighted or; unweighted ltoiiwhich the support and'lcontrol H5 extend downwardly wires m; H5, are connected or 'directlyattached or of which they form apart; that means as a whole may be regarded as a s'upporting and control line of which the wires Ila, H5, form apart or a continuation; The term line" is used in that sense in the following claims, without any mounted on the body and adapted to engage the pipe'wall'to lock the body against relative downward movement in the pipe, said second gripping means being movable with relation to 'the body "between a position out of pipe en- 'gage'ment and a position 'in pipe engagement,

and means urging the second gripping means from the non-engaging to the engaging position;

plug placing and setting means comprising a detent receiving passage in the plug body extending across the path of movement of the second grippingmea'ns, a supporting and control line,

a detent which forms a continuation of said line and is adapted to'lie in said receiving passage across said path of movement-ofnthe gripping #means to hold that 'grippingmeans in nonengaging position,

and means forming a party of the detent and line and normally holding the detent i'n'said passage,-said' lastnamed means 1 being releasable by' an upward pull exerted on the supportingand control line.

l. 2. Plug placing and setting means as defined in claim 1 and in which the supporting and control line comprises, atleast in part, aflexible wire, and the detent forms a part of the same ilexiblewire;

j [1 3. Plug pl'acingtand setting means as defined in claim 1 and in whichthe detent and the supporting and control lineat least in part are por- .c ,rtions of a length of flexible wire, and in which .the detent holding means is formed .as a bent 4. In settable pipe plugs of the type which include a-plug body, grippingv means mounted on the body adapted-toengage a pipe wall to lock the body against relative. upwardmovement in .,the pipe, an upwardly and Ioutwardly extending guide inthe body,. a pipe-wall gripper movable ",along said .guide from a lower position-out of engagement with the pipeto an upper'pipe engaging .position, and means urging the gripper upwardly-along the guide; plug placing and setting means comprising a detent receiving passage in the plug body extending across the path of I movement of the gripper, asupporting'and' control line; a detent which form a continuation of said line and is adapted t0 lie in the receiving passage-across the. path of movement of the gripper-to :holdthe-gripper'inits lower position; and? means forming a'--par.t of'the detent and line and normally holdingithe detent in the passage; saidr last named means being releasable by an upwardpuilfexerted on the supporting and control dine:

5.Plug'placing' andsetting means as defined in claim": 4 and in WhiCh the detent and the supportingand'controlline at least in part are portions of a; length of flexible 'wire.

6. Plug placingfand setting means as defined claim 41in which the detent and-the support- 9 ing and control line at least in part are portions of a length of flexible wire, and in which the detent holding means is formed as a bent portion of said wire.

7. In settable pipe plugs of the type stated in claim 1 and which also include a vertical va1ve seated passage through the plug body and an upwardly closing valve controlling that passage: plug placing and setting means as defined in said claim 1 and also comprising a detent connected with the supporting and control line and adapted to lie removably in a' position between the valve and the valve seat.

8. Plug placing and setting means as defined in claim 7, and in which the valve detent, and the supporting and control line at least in part, are portions of a length of flexible wire.

9. In settable pipe plugs of the type stated in claim 4 and which also include a vertical valveseated passage through the plug body and an upwardly closing valve controlling that passage; plug placing and setting means comprising a detent receiving passage in the plug body extending across the path of movement of the gripper, a supporting and control line which at least in part is in the form of a flexible wire a portion of which is adapted to lie in the detent receiving passage across the path of movement of the gripper to hold the gripper in its lower position, and a bend in the flexible wire engaging the body and adapted to releasably hold the end portion of the wire in the passage.

10. A settable pipe plug of the type described, comprising a plug body having upper and lower heads, a plurality of vertically extending guide members extending between and secured to the heads, and each of the guide members having an upwardly and outwardly extending guide and a downwardly and outwardly extending guide; pipe grippers movable in said guides, springs urging the upwardly-and-outwardly-movable grippers upwardly along their guides, a detent receiving passage in each guide member extending across the path of movement of the upwardly movable grippers, a supporting and control line, a plurality of detents formed as extensions of the line and adapted to be positioned in the detent receiving passages to hold the upwardly-and-outwardly-movable grippers in lower positions in their guides, and means associated with the detents to normally hold them in the passages, said means releasable by an upward pull exerted on the supporting and control line.

11. A settable pipe plug as defined in claim and in which the several guide members are spaced from each other in open formation about an open central space, in which the upper head has a central opening through it, and in which the detents are formed as parts of flexible wires extending down through the opening and extending their ends into the detent receiving passages.

12. A settable pipe plug as defined in claim 10 and in which the several guide members are spaced from each other in open formation about an open central space, in which the upper head has a central opening through it, and in which the detents are formed as parts of flexible wires extending down through the opening and extending their ends into the detent receiving passages, and in which the detent holding means are formed as bends in the flexible wires engaging portions of the guide members.

13. A settable pipe plug as defined in claim 10, and in which the detent receiving passages extend through the guide members from one face to an opposite face, in which the detents are formed as parts of flexible wires which are parts of the supporting line, the detent wires extending through the detent receiving passages and protruding their ends beyond one guide member face, and in which the detent holding means arebends in the protruding ends of the detent wires.

14. A settable pipe plug as defined in claim 10 and in which the several guide members are spaced from each other in open formation about an open central space, in which both upper and lower heads have central openings which, with the open central space, form a vertical passage through the plug body, a valve seat and an upwardly closing valve associated with the vertical passage, and in which the supporting line has flexible wire extensions which form the detents and also extend to positions between the valve and valve seat.

15. A settable pipe plug of the type described, comprising a plug body having upper and lower head plates with central openings through them, a plurality of vertically extending guide members extending between and secured to the head plates, said guide members spaced in open formation about an open central space which, with the head plate openings, forms a vertical passage through the plug body, a valve seat and an upwardly closing valve associated with one of the head plate openings, each guide member having its upper part formed as an upwardly and outwardly extending guide and its lower part formed as a downwardly and outwardly extending guide, upper and lower pipe grippers movable in the several guides, springs urging the upper grippers upwardly, detent receiving passages in each upper guide extending through the guide across the path of movement of the gripper therein and extending from a guide face which is adjacent the central body space to an opposite outer guide face, a supporting and control line, flexible wires forming parts of the line, the line extending through the upper head plate opening and the ends of some of the wires extending through the detent receiving passages with their ends protruding beyond an outer guide face, the protruding ends of the wires being bent to form holding means releasable by a pull exerted on the supporting line, and, some of the wires extending between the valve and valve seat.

16. A settable pipe plug as defined in claim 15 and in which the pipe grippers are formed as rollers with central pins which engage the guides.

ORIE O. DALE. JOHN D. CHESNUT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 903,314 Porter Nov. 10, 1908 932,766 Daniels -Aug. 31, 1909 1,092,508 Robinson Apr. 7, 1914 1,137,205 Hall Apr. 27, 1915 1,809,080 Sweet et al. June 9, 1931 2,249,172 Quintrell July 15, 1941 2,383,453 Crickmer Aug. 28, 1945 

